<?hh <<__EntryPoint>> function main(): void {
$socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
if (!$socket) {
    die('Unable to create AF_INET socket');
}
if (!socket_set_nonblock($socket)) {
    die('Unable to set nonblocking mode for socket');
}

$address = '127.0.0.1';
try { socket_sendto($socket, '', 1, 0, $address); } catch (Exception $e) { echo "\n".'Warning: '.$e->getMessage().' in '.__FILE__.' on line '.__LINE__."\n"; } // cause warning
if (!socket_bind($socket, $address, 1223)) {
    die("Unable to bind to $address:1223");
}

$buf = null;
$from = null;
$port = null;
var_dump(socket_recvfrom($socket, inout $buf, 12, 0, inout $from, inout $port)); //false (EAGAIN - no warning)

$msg = "Ping!";
$len = strlen($msg);
$bytes_sent = socket_sendto($socket, $msg, $len, 0, $address, 1223);
if ($bytes_sent == -1) {
    die('An error occurred while sending to the socket');
} else if ($bytes_sent != $len) {
    die($bytes_sent . ' bytes have been sent instead of the ' . $len . ' bytes expected');
}

$from = "";
$port = 0;
$bytes_received = socket_recvfrom($socket, inout $buf, 12, 0, inout $from, inout $port);
if ($bytes_received == -1) {
    die('An error occurred while receiving from the socket');
} else if ($bytes_received != $len) {
    die($bytes_received . ' bytes have been received instead of the ' . $len . ' bytes expected');
}
echo "Received $buf from remote address $from and remote port $port" . PHP_EOL;

socket_close($socket);
}
